4+4+15-20=8x2-28

Solution for 4+4+15-20=8x2-28 equation:

4+4+15-20=8x^2-28

We move all terms to the left:

4+4+15-20-(8x^2-28)=0

We add all the numbers together, and all the variables

-(8x^2-28)+3=0

We get rid of parentheses

-8x^2+28+3=0

We add all the numbers together, and all the variables

-8x^2+31=0

a = -8; b = 0; c = +31;
Δ = b2-4ac
Δ = 02-4·(-8)·31
Δ = 992
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{992}=\sqrt{16*62}=\sqrt{16}*\sqrt{62}=4\sqrt{62}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-4\sqrt{62}}{2*-8}=\frac{0-4\sqrt{62}}{-16}
=-\frac{4\sqrt{62}}{-16}
=-\frac{\sqrt{62}}{-4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+4\sqrt{62}}{2*-8}=\frac{0+4\sqrt{62}}{-16}
=\frac{4\sqrt{62}}{-16}
=\frac{\sqrt{62}}{-4}
$